Balotelli joined Liverpool from Milan in the summer of 2014 but after a dismal season at Anfield the controversial Italian striker has rejoined the seven-time European champions on a season-long loan deal.
Milan have made the deal official on their website and after emerging from a medical early on Tuesday morning Balotelli told reporters: "I'm happy to be back. This club is in my heart and I always hoped to play here again.
"Physically, I'm in good condition, I just have to get training with the squad."
Asked about his motivation, he said: "I've got plenty, but now is not the time to talk, it's time to get to work."
As for the future, he added: "I have to start work from today and to have a good season. Then we'll see what happens."
Balotelli's failure to spark at Liverpool has also left his international career in tatters. He has yet to feature in any games for the Azzurri during qualifying for the 2016 European Championships in France next summer.
Yet it remains to be seen if the 25-year-old, who has often been accused of wasting his playing talent, can resurrect his career this season.
Balotelli, who began his career with city rivals Inter Milan before moving to Manchester City in 2010, was feted by the vast majority of Milan fans when he joined the Rossoneri in January 2013.
But the striker's second spell at Milan is not being met with the same fervour - among fans, or in the media.
Recent polls have shown an overwhelming majority of fans to be against Balotelli's return to the club. On Monday night a survey on the popular Processo del Lunedi' football show on Rai television indicated that close to 62 percent of fans were against Balotelli's return.
Former Milan midfielder Zvonimir Boban, a respected pundit on Sky Sport who is often brutally honest in his opinions on football matters, called the club's decision to take the player on loan "totally absurd".
Boban had previously stated: "Let's stop talking about him, he's never achieved anything."
Last week, the former Croatian international hit out: "I wish him all the best, but he's never really taken off as a player. If he returns (to Milan), it is totally absurd."
Milan, along with city rivals Inter, failed to qualify for Europe this season and both clubs face a make-or-break season after several years of underachievement.
Sinisa Mihajlovic has taken over the reins at Milan following the sacking of coach Filippo Inzaghi and he is expected to whip the Rossoneri into shape this season.
Milan began the Serie A campaign with a 2-0 defeat at Fiorentina on Sunday when Rodrigo Ely was sent off in the first half and fellow central defender Alessio Romagnoli gave away a penalty to La Viola in the second half.
Milan's opening game of the season is against Empoli on Saturday.